Comment by isoprophlex

An entire integrated explosive device + detonator + radio circuit that leeches off the host device's power supply, that you activate by blasting an area with some out-of-band signal on a frequency that propagates far and wide?

Takes some upfront work but you don't have to mess with the device, any firmware that might leave traces, and the comms network itself. You just fly a big antenna nearby and everything goes boom.